There are a variety of shower curtain and tub liner patents which concern themselves with a fastening means to secure the top, bottom or sides of a sheet. As is shown below however, none of these patents solved the problems which result along the lower portions of a limp film, shower curtain. i.e., the film billowing away from the shower walls, shifting sideways when contacted, and clinging to skin of the person, when affected by forces on the inside of the shower.
A patent that pertains to a fastening method is U.S. Pat. No. 4,088,174 (Edwards) Shower Curtain Anchor Attachment, that attacks the inherently negative properties of a limp shower curtain with a complicated anchoring device which guides the lower edge of this shower curtain by means of a track system. Edwards' reference retains the shower curtain through two, circular snap apart discs. This disc cover has a centrally-oriented protuberance that is perpendicular to the disc cover and the disc body and perpendicular to the back wall. Essentially, Edwards has constructed a flexible shower door, which, (while effective for its purpose), did not solve billowing problems that are inherent in limp film shower curtains. The need for a solution to the billowing and sideways moving, clinging shower curtain remained unmet.
U.S. Pat. No. 3,365,684 (Stemke) Shower Curtain Retaining Means; is a series of magnetic mountings used to secure and retain the edge of a shower curtain to the side wall of a shower enclosure. Though less complicated Stemke was still a mechanical device in the form of a plurality of magnetic elements, adapted to be mounted in a spaced relation on the loose end of a shower curtain, and on the adjacent bathing area defining the side wall, to maintain the end of this curtain in closing relation with the wall to prevent any water splashing outside the bath area. The solution again, (a mechanical device), never solved the inherent problems of billowing, shifting sideways liner movement and clinging when the shower curtain is affected by forces on the inside of a shower.
Patent NL 8400-060-A, a Shower System with Magnetic Elements Along the Bottom of a Shower Curtain is a very simple mechanical device that utilizes pairs of magnetic elements to hold the bottom of a shower curtain which prevents any water from exiting the enclosure and prevents the shower curtain from clinging to the skin of the person showering. Although much simpler, it's still a mechanical device which never solved the problems of billowing along the lower portions of a limp shower curtain when water flowing out of the shower head generates forces on the inside of the shower enclosure. Thin, limp and flimsy shower curtains always exhibit the inherently negative properties of billowing, shifting side to side motion, and clinging, when lower portions of such liners are affected by forces on the inside of a shower enclosure. It is noteworthy to point out, that each of these devices pose a swallowing or choking hazard to children, who; because of their innate curiosity, will invariably separate simple mechanical devices. Unfortunately, small complex parts are easy to lose and hard to find.
These three references discussed above, cover a mechanical, magnetic or adhesive means that prevents the lower portions of a shower curtain or liner, from being pulled away from the bottom of the tub or shower walls. But, the solution in each of these references was some sort of secondary device which was used in conjunction with a shower curtain to retain it or prevent it, from billowing away from the shower wall; a problem that each inventor cited as the negative characteristic his device had solved. But none of these inventors ever solved the problems inherent with limp, flimsy plastic film liners. Their partial solutions resolved problems with complex hardware, however, they were incomplete solutions to the problems of limp and flimsy shower curtains, billowing and moving sideways at the bottom of the shower when in use. The problems that result along the lower portions of limp plastic films placed in a shower enclosure, i.e. billowing, side to side motion and clinging are negative characteristics inherent in thin flimsy films, that are not solved by the inventions. These inventions are only fastening devices, which "treat the symptoms, but do not cure The disease." The use of these fasteners, while they do deal with liners, does not solve the problems. The need remains for a solution to the inherently negative problems which result, when a limp plastic film is placed in a shower enclosure, i.e.. billowing, shifting sideways movement and clinging of the liner to the skin.
U.S. Pat. No. 4,671,026 a Bathtub Wall Surround Kit and Seal, (Wissinger), essentially creates a new set of walls in place of the existing shower walls which are usually replaced due to deterioration. The Bathtub Wall Surround Kit and Seal is a rigid physical structure that is not removably attached. The benefit of not having to grout and caulk the tiled walls frequently is what this invention really offers. The wall surround kit and seal has all of the same problems that tiled shower walls do, they have to be cleaned.
U.S. Pat. No. 2,809,379 a Portable Shower Stall is a circumferential shower curtain, that again, is only an elastic film which has all the associated problems of billowing and sideways movement, which result when air currents created by flowing water cause a partial vacuum in the shower enclosure. It does not allow the full use of the tub/shower area, and it also necessitates an ugly mechanical frame which is mounted above the user's head. It requires tubular rings which enable the top of this shower curtain to encircle the bathtub, which in effect, creates a shower enclosure. It does not line the shower walls--it is the shower walls! It normally surrounds old style, free standing tubs used for bathing, not for showering. The invention allows a conventional tub to be used as a shower, but, because a thin film now encircles the showerer, billowing, sideways movement and clinging of the flimsy liner to the skin, is even worse than when a conventional shower curtain is used. In a worst case, the film partially wraps around a person showering. The need for a solution to these problems is exacerbated by this invention, not solved.
U.S. Pat. No. 3,938,200 a Contamination Prevention Systems for Bathtubs (Roberts), is a flimsy elastic sheet. It's a biological barrier that cannot be contaminated prior to use by contact; it has a closed bottom, the bottom has to be punctured to drain the tub, and it has to be replaced after every use. Once the Roberts invention is wet, it is very slippery and too dangerous to be used for anything other than tub sit-down bathing, (because of the hazard of slipping and falling). This is the major flaw with Robert's invention. Because it has a closed bottom, it has exclusively a tub use. Once wet, this thin flimsy film is Just too dangerous to stand on. Roberts' closed bottom tub liner has to be punctured for drainage each time the patient is finished bathing. If Robert's liner had a hole in it for drainage prior to bathing or had an open bottom the film would float up to the surface of the water in the tub and be rendered useless as a contamination prevention system.
It is to be emphasized that the limp and flimsy film material used in Robert's bathtub liner does not even loosely conform to, never mind permanently retain, the contours of the shower walls; (where the sill of the tub or floor of a shower stall, meets the bottom of the shower walls). The only reason Roberts' flimsy plastic sheet is even in contact with the sides of the tub, is because water in the tub is pushing the film against the sides of the tub. The only portion of Roberts' bathtub liner that can conform to the contours of a tub, is that portion of his liner in a tub that is filled with water. It's important to remember that the portions of Roberts' tub liner that are above the sill of the tub do not even loosely conform to the contours of a tub, where the sill of the tub meets the bottom of the shower walls. It is the outward force of the water in the tub, that is pushing Robert's liner against the sides of the tub. Without the weight of water in a tub holding his liner in place, his liner springs upward and exhibits elastic recovery. Even if Roberts' tub liner had the open bottom: (which is contrary to his teachings), the sides of such a liner cannot be held securely against the tub or shower walls, by the force of water alone. It is also very important to remember that if Roberts' liner has the open bottom, it is not a biological barrier, and cannot be used as a contamination prevention system. His concept fails if a hole is made at the bottom of his liner, because rising water in the tub will cause his liner to float up to the surface. This also renders the liner useless as a contamination prevention system. And, if the closed bottom concept is used and the film is slit along the center of the bottom of the type of liner, both long slit edges of film float up to the surface as well.
An even worse-case scenario for the open bottom Roberts liner would be using it to cover the walls above a tub or the walls of a shower stall. If Roberts' closed bottom concept was placed in a shower, the sides of this closed bottom liner could not be held against the walls of the shower by the outward force of water. No amount of water; (no matter how deep), will ever stop the lower portions of his thin, flimsy tub liner from billowing, clinging or moving sideways, because instead of floating up to the surface vertically: (which happens when it is used in the tub and you make a hole in it), the Roberts liner merely moves back and forth, away from the shower walls in direct relation to the water moving around in a tub. Roberts' closed bottom bathtub liner concept was never designed to and is incapable of covering the walls above the tub, because it is just too dangerous to stand on once it becomes wet. If Robert's tub liner is made with an open bottom and used in a shower it cannot overcome the three-dimensional forces, rotational forces and forces in the x, y and z directions which pull the liner into the person showering, because it is only a limp and flimsy film. The partial vacuum caused by water generated air currents cannot be overcome by Roberts' thin and flimsy, unrestrained bathtub liner. If the open bottom concept is attempted by slitting the center of Robert's flimsy liner, the edges float up from the bottom of the tub as the tub is filled with water. Robert's closed bottom, flimsy bathtub liner cannot be used to cover the walls of a shower for four reasons:
1st, The thin film is flimsy and limp: it cannot permanently maintain its shape or position without some means of restraint.
2nd, the liner must be replaced after each use.
3rd, the closed bottom liner has to be punctured after each use to drain waste water. If punctured prior to use it is not a biological barrier and cannot be used as a contamination prevention system, and
4th, once wet, it is too dangerous to stand on.
The need for a liner which covers the walls above a tub, or the walls of a shower stall that will not billow away from the shower walls, not move sideways when contacted, and not partially cling to the skin of the showerer when affected by forces on the inside of the shower enclosure remains unmet.
U.S. Pat. No. 4,263,347 Apparatus and Method for Masking Surfaces, (Banta), is a thin, limp plastic film, which is fastened at the very top of a wall by use of an adhesive strip that is attached to the upper edge of the flimsy sheet of plastic film material. Banta's device cannot resist, never mind overcome, three-dimensional and rotational forces because it is only a folded up and rolled sheet of limp plastic film, attached at the very top of a wall with a continuous strip of adhesive tape. The inventive feature of Banta's device is this strip of adhesive tape which is attached to the very top of this rolled plastic sheet, and used to hold the upper edge of this film against a wall. Clearly, Banta has developed claims which cover this continuous strip of adhesive tape along the top of his limp plastic sheet which is folded, but, the adhesive strip which is attached to this sheet is a critical part of his invention. Banta's device did not solve the problems which result along lower portions of a thin film, shower wall liner placed in a shower enclosure, i.e., billowing, shifting sideways motion, and clinging. Banta's reference cannot overcome the three-dimensional and rotational forces which will affect the lower portions of his wall cover, (if It were used in a shower), even though it is securely fastened at the top, because it's only a flimsy sheet of plastic film and the lower portions are not restrained, Billowing, clinging and shifting side to side motion always occurs along the lower portion of Banta's liner because his cover is only a limp and flimsy sheet of thin plastic film.
Using mechanical, magnetic or adhesive fastening means cannot solve the problems that are inherently negative characteristics of thin, flimsy plastic films. These basic problems are not solved by the user, of these fastening devices, and the need for a solution to these problems remains unsolved.
Looking at just film liner properties, thin and limp, unrestrained plastic films are inherently flimsy and rebound if deformed as soon as the force is removed. This is due to Elastic Recovery, an inherent property of thermoplastics and thermoplastic films to resists permanent deformation; and this limpness is an effect of molecular shape. Thin flimsy films exhibit elastic recovery because they have a very low modulus of elasticity. The Tool and Manufacturing Engineer's Handbook, Volume 3 c 1985, defines Modulus of Elasticity as: ". . . [T]he ratio of stress to strain" within the elastic range of a material; a measure of stiffness; the ability to resist deformation." In most typical plastics, the molecules are not aligned and resemble a pile of spaghetti. This is a good model for low density polyethylene. As a result of this scramble of molecules all being pulled in different directions, the molecules will not dead-fold. Dead-folding is very important since it enables a sharp shape to be held. Despite this lack of a dead-fold property, however, the transparency, water impermeability, and low cost of polyolefin films make them an attractive material for use in a number of applications, such as a shower wall liner.
The term dead-fold is defined as: "the property of a material to retain a sharply creased fold." It is shown by a material deformed by a force which is greater than the modulus of elasticity such that the deformation is permanent and which resists returning to its original shape; i.e., the material will not yield easily once it has been dead-folded. In a high density polyethylene, (HDPE), the molecules are more aligned and more closely resemble pencils in a roughly oriented pile. HDPE will fold a bit better, but, the fold still does not lay flat and it is not retained over time. HDPE however, is very susceptible to tearing since it is so highly oriented.
As noted, plastics are too elastic to be dead-folded, since they have too low a modulus of elasticity. But metals, on the other hand, will dead fold and are materials which can be formed into shape and then permanently retain their shape and not rebound when the force is removed. This property is inherent in metals, materials which are not extensible at low pressures, and this is because the atoms of metals resemble spheres, in contrast to the strings of plastic molecules, This may be visualized by considering how beads may easily shift position and have no tendency to hold back movement, unlike the movement of strands in a pile.
Unlike plastics, however, the atoms of metals slide past each other. This is why a metal foil, when folded, stays totally folded. Materials like metal foil or aluminum foil have very high moduli of elasticity and deform in a permanent manner when stressed beyond a critical point. Table 1-1 of the Tool and Manufacturing Engineer's Handbook makes this comparison: . . . [T]he Modulus of Elasticity of Thermoplastics is 0.17-28. In contrast the Modulus of Elasticity of Aluminum Alloys is 69-79 GPa. More simply stated from The Plastic Engineer's Handbook of the Society of the Plastics Industry, 5th edition, c 1991, ". . . IT]he Modulus of Elasticity for metals is 10 to 60 times greater than that of plastics."
The combined use of dissimilar materials can produce new materials having enhanced properties which may be used to solve problems by taking advantage of the positive properties of these newly created materials and defeating the negative characteristics that are inherent in the materials when used individually. The Encyclopedia of Materials Science and Engineering, c 1986, Section 2, Composites states: ". . . [A]mong the most significant uses of plastics in building materials are composites, combinations of materials whose properties transcend those of the individual materials acting alone.
There are many patents that cover combinations of materials which use plastic, foil and rubber, in new, inventive and unobvious uses. For example,
U.S. Pat. No. 5,096,759, (Simpson); a Laminated Roofing Sheet, is a thin layer of foil material attached to conventional roofing material which serves to reflect infrared and ultraviolet radiation where ". . . [r]eflected infrared rays reduce the heat transmitted to the roofing surface by the sun". While the foil of Simpson's device is not structurally strong; as Simpson states from his Summary of Invention, on page 1, lines 4-6, ". . . [T]he aluminum may be relatively thin and very flexible, because it is not intended to serve as a strengthening element", and from his Summary of the Invention, page 1, lines 12-14, that, ". . . IT]he polyethylene film is to provide the structural integrity of this roofing sheet", and from his Description of the Preferred Embodiments, page 3, lines 12-13, it states, (regarding his use of this aluminum foil), that it is, ". . . [a]n aluminum foil sheet having a desired thickness of about 0.0007 inches", it is clear that combinations of different materials can create properties that transcend those of the individual materials acting alone.
U.S. Pat. No. 2,847,948 Composite Roofing Strip, (Truitt) is a roofing material where the foil is used to withstand deterioration and also because of its ability to resist the penetration of heat into buildings. Truitt teaches the use of foil as: ". . . [a] protective metallic sheet" where ". . . It]he exposed roofing or siding surface is essentially all metallic." In this case, even though the aluminum foil was used in a roofing application that was similar to the invention of Simpson, (where heat reflective properties of the foil are taken advantage of), it was used in an unobvious way to solve the problems of exposed films being subject to UV degradation. While shielding, not heat reflectivity is the compelling claim of Truitt, his use of similar materials in a non-obvious way did not preclude patentability of his invention.
Another interesting use of film and foil is U.S. Pat. No. 4,477,509 (Mott), Disposable Lid for Pots, Pans and Like Receptacles. This disposable lid for covering and containing food: (as it is heated in a cooking vessel), uses a foil to restrain the contents of heated food from spilling over into an oven. Mott's use of a foil with film: (as was the case with Simpson), was primarily for its heat reflective properties. In Mott, it is the film which adheres to the surface portions of the food receptacle, not the foil. The foil used in Mott has no strengthening properties at all because the lid is a plurality of layers of flexible material; an outer layer that is heat reflective foil and an inner layer which is a thin, food service film. These two thin materials are not adhesively or heat sealed to one another, as shown in claim 4 of Mott, which'states: ". . . [a]re adhered one the other by direct surface contact of at least portions thereof, without the benefit of intervening materials to produce adhesion there between", but are simultaneously drawn together from two separate compartments of a very simple device and are in superposed contacting relation. The adherence here, of the film to the food receptacle is by direct contact. Since the metal layer is not attached to the plastic layer, there is no tie between the individual layers.
Often seen in construction, separate unattached and independent layers are not strengthening in nature. Look at several sheets of plywood stretched and flexed, When you glue or nail the sheets together a much greater force is needed to flex them. The layers independently would not work in the present invention and must be mutually attached. If foil is used with a liner, as it is in the Mott reference, it will billow. The primary objective of Mott's invention, in his use of foil is to prevent the food film, during heating, from bursting and thereby having heated food contents spill into the oven. As food is heated in the Mott covering device, his foil layer serves to restrain and protect the poly film from bursting. This is stated in Mott's Summary of the Invention. page 4, lines 54-55: ". . . [i]s to provide a disposable lid capable of creating and maintaining a steam dome for the contents of a receptacle, subject to cooking, baking and heating at elevated temperatures." Although Mott's use of the foil did not produce a rigid member, his device did take advantage of the deformable properties of aluminum foil: (in contrast to Simpson and Truitt), who used foil to reflect heat and as a shield, respectively. The lack of a tie between Mott's layers of film and foil, however, make it impossible for rigidity or structural strength to be imparted to the materials. Mott's combined use of film and foil did not produce a rigid member either, because the two materials, although used together, in actual practice work independently of each other. The elastic properties of a food film permit a controlled expansion as heated contents create a steam dome. The temperatures and pressures exerted on this food service film, however, reach the point where the elastic properties of the film can no longer contain the hot expanding materials in the vessel. It is at this point that the foil works to contain the expanding steam dome by preventing it from rupturing or exploding and spilling the hot food contents into the oven. In actual practice, Mott's film and foil layers work separately and separate unattached layers are not strengthing in nature. The mere use of an attached or encapsulated combination of materials: as shown in Mott's reference, does not impart rigidity or structural strength. Multiple layers of a limp material remain basically limp and are not rigidified through mere encapsulation. Foil itself is not rigid in an unbent form. Mere encapsulation with other materials will not impart rigidity or structural strength. A flat, one-dimensional unconnected foil member is not rigid or structurally strong.
U.S. Pat. No. 3,628,721 a recloseable package member, (Palmer), is a tubular or circular, food storage container which is repeatedly opened and closed by bending a thin and narrow strip of aluminum foil across its width. Palmer's deformable package is intentionally designed to be easily and repeatedly opened and closed: i.e., it will yield easily. This is because there are no forces affecting the inside of Palmer's container and that is why Palmer only uses a thin and narrow strip of aluminum foil and only radially creases it. Palmer uses just enough aluminum foil to hold a radiused crease, and this flimsy, one-dimensional creased member cannot overcome the forces on the inside of a shower enclosure.
Palmer's recloseable package member only takes advantage of the deformable properties of a thin, narrow strip of transversely creased aluminum foil, and thus, only confers a minimal property in the widthwise direction.
The thin and narrow strip of aluminum foil, used by Palmer, can only keep his bent tubular container from becoming undone, but, only as long as no force acts on it. Palmer's deformable package cannot be made rigid or structurally strong for the following reasons:
1. Palmer anticipates only an external unfolding force, and is ineffective in resisting the forces which act on the inner surface. As soon as even a small force is applied to Palmer's package member, (as opposed to the seal area), it yields.
2. Palmer's deformable strip is longitudinally oriented and repeatedly deformed. It is not a rigid member.
3. Palmer is only a one-dimensional, deformable element, It is not a three-dimensional structure:
4. The Palmer deformable package is weakened by repeated bending and unbending, thus no structural strength is ever imparted or achieved in the Palmer package; and
5. Palmer's thin and narrow, repeatedly creased aluminum foil member is bent in the wrong direction for rigidity. If forces existed on the inside of Palmer's deformable package, they could not be overcome.
Because Palmer requires the deformable member to be easily and repeatedly opened and closed, resistance to a rotational force is a property that Palmer absolutely does not want. And that is why his thin aluminum strip; as he states from pg. 4, lines 64-65, ". . . [n]eed only be wide enough to allow facile folding longitudinally".
Palmer teaches a thin and narrow strip of foil used on a sheet of film that is repeatedly bent back and forth to open or close a food storage container. Palmer calls this repeatedly deformed, aluminum foil strip, a "structure". But, the true use of the term is more commonly associated with rigidity and strength. A Truss, a Spar, or an I-Beam, for example, are said to be structures. Palmer's repeatedly deformed, radially creased member is clearly not a structure in mechanical terms.
From Kent's Mechanical Engineering Handbook, 12th Edition, c. 1950, "Structure" is defined as ". . . [a] combination of resistant bodies capable of transmitting forces or carrying loads, but having no relative motion between parts."
Palmer's recloseable package member is a limp sheet of plastic film with a very thin and narrow strip of aluminum foil, repeatedly transversly creased into a circular food storage container. Palmer's device is not a combination of resistant bodies capable of transmitting forces or carrying loads. Palmer uses only enough aluminum foil, (in thickness and in width), to hold the radiused crease which keeps his package from unfolding. It is important to note, that Palmer's mere holding of a radiused crease did not impart strength. "Strength", is defined as: ". . . [T]he power to resist force, strain or stress without yielding or breaking." This, however, is contrary to Palmer, who requires his aluminum foil strip to be easily and repeatedly opened and closed. Palmer's radially creased, aluminum foil member is merely a weak, one-dimensional deformable element, which by design and intention, yields very easily. It is not structurally strong. In fact, by definition, Palmer's device is not even a "Structure", because it is not a combination of resistant bodies capable of transmitting forces or carrying loads. In simple mechanical terms, Palmer's thin and narrow, repeatedly deformed aluminum foil member is not a physical structure.
it is important to remember that after contents of Palmer's package are removed and the package reclosed the location of his radially creased member changes, but most importantly, repeated bending and unbending of a thin and narrow strip of aluminum weakens the material.
There are materials that do crease, but are so soft: (gold leaf, for example), that they cannot become rigid or structurally strong. Palmer's use of the term: "Structure" is inaccurate, because he prefaces this term with the word deformable: which when associated with the term structure, does not connotate structural strength. A structure is a combination of resistant bodies capable of transmitting forces or carrying loads, but having no relative motion between parts. "Strength" is defined as the quality of bodies by which they sustain the application of force without breaking or yielding. Palmers use of the term: "structure", refers only to his combination of two materials.
Because Palmer's repeatedly deformed member is not a physical structure: as the term is generally used, it cannot resist forces. In reality, Palmer's recloseable package member is the exact opposite of a structure since it is designed and expected to yield very easily. If forces existed, on the inside of Palmer's recloseable package, they could not be overcome by this weak, one-dimensional member. It is clear, from Palmer's deform-able, recloseable package, that merely creasing a thin and narrow strip of aluminum foil across its width, does not create a member that is rigid, and cannot produce a member that is structurally strong.
While it is clear that many products which use plastic film and foil together have been used in new and distinctly/clearly unthought of ways to attack problems that no one had previously solved, it is also clear that the specific characteristics of the materials used along with their method of application, create definite limits in the capabilities of these combinations. The use of similar materials for other non-obvious uses; or in different applications, does not eliminate patentability. One combination of materials alone is not a solution to all problems, as shown by Palmer's limited use, repeatedly deformed, transversely creased aluminum foil strip.
Looking at this prior art in light of a liner, the lower portions of an unrigidified or unrestrained, thin film shower wall liner always exhibit the following negative characteristics which have not been solved by the prior art. When affected by forces on the inside of a shower enclosure the lower portions such liners do the following negative things:
1. They billow away from the shower walls,
2. They move from side to side,
3. and they cling to the skin of the person showering.
There remains a need for a shower wall liner made from a thin plastic film whose lower portions, when affected by the forces on the inside of the shower enclosure, will:
1. Not billow away from the shower walls,
2. Not move from side to side,
3. Not let water under the liner, and
4. Be restrained from clinging to the skin.
These needs are presently unmet.